1. Field of the Invention
The present invention relates to a rolling piston type rotary compressor including an inverter controller for use in an air conditioner or a refrigerator and, more particularly, to a rotary compressor designed to ensure reliable operation as well as to reduce vibrations of a rotary shaft.
2. Description of the Relevant Art
A conventional rotary compressor of the rolling piston type typically includes upper and lower bearing assemblies by which a rotor of motor is journalled in a cantilever fashion. Japanese laid-open patent publication No. Showa 61-229988 discloses a rotary compressor wherein an upper bearing is adapted to rotatably support one end of a rotary shaft in a motor and is fixedly connected to a stator of the motor. Japanese laid-open patent publication No. Showa 61-31683 also discloses a rotary compressor wherein a rolling bearing is provided at the upper end of a rotor. The inner diameter of the rolling bearing is greater than the diameter of a rotary shaft, and the inner ring of the rolling bearing is not integrally fixed to the rotary shaft. Another rotary compressor, as disclosed in Japanese laid-open utility model publication No. Showa 56-139886, includes a bearing assembly situated above a motor to jouranal the upper end of the rotary shaft.
Although the upper end of each rotary shaft bearing in the prior art rotary compressors, no attempt has been made to provide the manner of lubricating such bearings when the motor is rotated at low and high speeds and reduce the amount of oil which may be discharged to a circulating system. Consequently, lubrication is not sufficiently effected when the motor is rotated at a low speed where fast pumping can not be expected as well as at a high speed. It is also to be noted that oil around the bearing by which the upper end of the rotary shaft is journalled tends to flow into the circulating system from a closed casing as gas is discharged therefrom. The discharge of the oil deteriorates the operation of a heat exchanger and thus a cooling cycle. In addition, such discharge of the oil results in a lower oil level, causing not only insufficient lubrication of vanes, but insufficient supply of the oil to the bearings as well. This results in unreliable operation of the prior art rotary compressors.
The manner in which the rotary shafts are journalled by the bearings used in the prior art rotary compressor in no way prevents inproper contact therebetween in the event of bending or any other form of deformation of the rotary shaft. Greater pressure is thus locally applied to the surfaces of the rotary shafts and the bearings. This results in an increase in the loss of sliding movement, and thus unreliable operation of the prior art rotary compressors.
However, no attempt was made in the prior art rotary compressor to prevent any loss of such sliding movement between the shafts and the bearings.